Ken Livingstone pledged to halt police cuts, protect Londoners from recession and offer more accountability as he officially entered the mayoral race.

The former mayor will need to fight off competition from ex-MP Oona King to become Labour's official candidate.

He filed his nomination form at the Labour Party headquarters.

Mr Livingstone was ousted by Tory Boris Johnson in 2008 after serving as the Mayor of London since 2000. Tottenham MP David Lammy is leading his campaign.

Dagenham and Rainham MP, Jon Cruddas, has also backed Mr Livingstone's bid to be the Labour candidate in the 2012 mayoral race.

A spokeswoman for Mayor Boris Johnson's office refuted claims that police numbers could be cut.

'Hold down fares'

Mr Livingstone said: "I want to do everything I can to protect Londoners from the recession and the effects of the new government's policies.

"Instead of Boris Johnson's wasteful projects we must concentrate on defending public services and holding down fares.

"We need to halt the present short-sighted policy of cutting 455 police officers and if elected mayor I will stop Boris Johnson's threat of cuts to the 630 safer neighbourhood police teams.

"I believe it is absolutely essential that the Mayor of London is accountable and regularly holds press conferences with the media.

"It is astounding that under Boris Johnson there are just two press conferences listed on the GLA website in the last year," he added.

He became involved in London politics as a leader of the Greater London Council in the 1980s. He went on to become an MP for Brent East in 1987 after the council was axed by the Conservative government in 1986.

When the office of the elected Mayor of London was formed as part of the Greater London Authority, Ken Livingstone was voted as its first incumbent in 2000.

Mr Johnson's spokeswoman said: "London's safer neighbourhood teams has played a vital part in reducing crime in the capital and will continue to do so in their current numbers under this mayor.

"However tackling crime in a city as diverse as London is a huge task and policing flexibility is a must if we want to continue to make the city safer."